After reading this post and also wanting to do the same I am thinking of what would be a best way to add royalties function to ERC721 by OZ. What I am aiming is that they are always used and can never be skipped, which can occur now if you look at above example from link.
So I belive it should be added in safeTransferFrom method, but as we want to have royalties cut directly in ETH paid for transfer, we need it to be payable? maybe we can also add that it can take eth but it can take cut in tokens paid as sometimes platforms offer possibility to buy NFT with some token.
Open for ideas and discussions.